Dispensed liquid measurement device

ABSTRACT

A measurement device containing one or more capillaries to measure the volume of a dispensed fluid and determine the volumetric accuracy of the dispensing device. The measurement device can contain a reservoir containing the fluid to be measured and there may be an additional reservoir for a secondary fluid. A viewing window is necessary to complete a manual measurement and may include a magnifying lens. The liquid well by the capillary inlet may be shaped such that the measurement fluid is directed toward the capillary. The well may have features designed to position the dispensing device toward the capillary, or to position the well proximal to the capillary after it is filled. The well may also have surfaces or coatings which attract or do not attract various types of substances. The measurement device may interface with sensors to output measurement data.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISK APPENDIX

Not Applicable

FIELD OF THE INVENTION

The present invention is in the technical field of fluid measurement andtesting.

More particularly, the present invention is in the technical field ofcalibrating or verifying the calibration of fluid dispensing devices.Some examples of these devices are, but are not limited to: pipettors,multi-channel pipettors, or automated dispensers. The present inventionmay be used to measure the accuracy of the device for aspirating anddispensing a specific volume of liquid. In particular, the field of theinvention relates to the confirmation that the device is correctlycalibrated such that the volume of liquid aspirated and dispensed isaccurate and repeatable within the error limits determined by themanufacturer of the device and international standards such as ISO17025.

BACKGROUND OF THE INVENTION

Liquid handling pipettors are an essential tool and are used extensivelyin laboratories across but not limited to such industries as academicresearch, applied testing, and medical diagnostics.

The purpose of the pipettor is to transfer specific volumes of liquidbetween containers. Examples of this action include but are not limitedto: the sub-sampling of patient liquid samples such as blood or urinefrom a patient sampling vessel to an analysis vessel such as the 96-wellmicrotiter plate; the assembly of individual reagents from master stocksto a tube containing a mixture or reagents such as would be used forpolymerase chain reaction (PCR); and transfer of tissue culture growthmedia from stock to individual cultures.

Pipettors by design are accurate at measuring specific volumes ofliquids. The volumes of liquids measured can range from nanoliters tomilliliters. Because of the extensive range of volumes measured,pipettors are manufactured to cover a subset of volumes such as but notlimited to: less than 1 microliter, 1-2 microliters, 1 to 10microliters, 10 to 100 microliters, 20 to 200 microliters, 100 to 1000microliters, 1 milliliter to 5 milliters.

In order for pipettors to accurately measure specific volumes, they mustbe routinely tested and calibrated. This routine testing and calibrationis extremely important and often specified in a laboratory's StandardOperating Procedure (SOP). Evidence of routine verification andcalibration of pipettors may even be subjected to audit by third partyorganizations such as those that regulate medical diagnostics andapplied testing laboratories.

Verification and calibration of pipettors is most usually donegravimetrically, by weighing the dispensed amount of a reference liquidsuch as water. This method requires the use of an extremely accurate setof weighing scales, such as a 6 decimal point scale used to measureweights as small as 1 microgram. These scales are themselves verifiedand calibrated against an external weight reference or calibrationdevice that has been certified as true and accurate measure of weight.

Another commonly used method is an absorbance-based system that utilizesa photometer and dual color dye as the basis of pipettor calibrationverification. One such system uses a known concentration of a dye thatabsorbs at one wavelength. The photometer determines the vialpathlength, and then a dye solution of known concentration and adifferent absorbance maximum is pipetted (using the pipettor to becalibrated) into the reference solution. The solutions are mixed by thephotometer and the absorbance is read. The photometer and softwareconvert the absorbance reading to the volume pipetted, and the result isprinted. After the user has taken the desired number of data points withthe pipettor, the device generates a printed result with statisticaldata that comprises individual sample volumes or replicates, mean volumeof all replicates, % CV (precision), and inaccuracy from target volume.The machines necessary for this method are fairly expensive.

The calibration process is arduous, time consuming, and prone toinaccuracies, particularly at small volumes where evaporation of waterand the propensity for water to adhere to plastics can introduce error.At these lower volumes, the movement of air currents across the pan of asensitive scale, or slight vibrations transmitted through a building'sstructure, can also introduce error in gravimetric analyses.

A typical gravimetric process involves repetitive weighing of a seriesof water volumes appropriate to the dispensation range of the pipettor,e.g. 2 microliters, 10 microliters and 20 microliters for a pipettorwith a stated range of 2-20 microliters. These measurements are often inthe range where environmental inaccuracies described above aresignificant (generally <100 microliters). The process would be repeatedat least 6 times to obtain a reliable accuracy for each volume: forexample, 100 microliters±2.0 microliters. At this volume the pipettorwould be said to have an accuracy of 100 microliters with a criticalvariance (CV) of ≦2%.

The pipettor is fitted with a disposable plastic tip that contacts theliquid being transferred. The underlying mechanism of the pipettor is apiston housed in a cylinder. As the piston moves downwards in thecylinder air is displaced. The piston is depressed to a specifieddistance by the action of the thumb pushing downwards on the top of thepiston or by a small electric motor and a drive assembly such as a wormgear. The pipette tip is inserted into the liquid to be transferred andthen the piston allowed to return to its original position; thedisplaced air is replaced by liquid, filling the pipette tip with therequired volume of liquid. The pipette and tip are moved to the targetvessel and the piston again depressed and the liquid ejected.Over-pipetting, i.e. depressing the piston slightly further than beforethe liquid was aspirated, ensures that all liquid within the pipette tipis ejected. The piston is returned to its pre-pipetting position and thedisposable pipette tip ejected.

The starting position of the piston and the distance the piston travelsis set by the user before the liquid is aspirated. The start position ofthe piston is set via a volume control wheel for manual setting ordigitally for a motor-driven electronic pipettor. The user simplyadjusts the volume control wheel or the digital display to display theintended volume to be transferred. The user proceeds to transfer thenominated liquid volume as described above.

Current verification and volume calibration involves confirming, bygravimetric or dye absorbance methods, that the selected volume shown onthe pipettor and the volume of liquid aspirated and dispensed areidentical with respect to target volume and CV of variance. If there isdisagreement between the selected volume to be dispensed and the actualvolume dispensed, then the pipettor is out of calibration. Before thepipettor can be used for routine laboratory use it must be calibrated toinsure the accuracy of the volume dispensed with respect to the selectedvolume shown on the pipettor.

While others have developed methods for collecting selected volumes ofliquids using the geometry of the capillary-type device, such as Kenneyin U.S. Pat. No. 6,531,098 and Karg et al. in U.S. Pat. No. 8,080,218,no one has invented an easy method of determining whether a desiredvolume of liquid is accurately dispensed.

The invention described eliminates the arduousness of determining if apipettor is within acceptable accuracy limits. It entails a simplemethod of validating the calibration of the pipettor, and, within theaccuracy limits of the device, performing the calibration. In addition,while current methods of calibrating pipettors indirectly determine thevolume dispensed, either by determining weight or the absorbance of adye contained in the dispensed liquid, this invention directly measuresthe volume dispensed by the pipettor. Thirdly, this invention allows forhigh throughput automation, with the device taking the form of astandardized microwell or microtiter plate.

SUMMARY OF THE INVENTION

The present invention provides a measuring device, which includes acapillary and a well for dispensed liquid, positioned such that theinlet end of the capillary can contact liquid placed in the well. Theentire measuring device, or just the capillary, could be disposable orreusable. Markings on the capillary or on the measuring device cancorrespond with the volume inside the capillary. The liquid dispensedinto the well, and subsequently drawn into the capillary, can beaccurately determined, by comparing the location of the liquid/airinterface meniscus with the markings. Alternatively, sensors coulddetermine the location of the meniscus or multiple meniscuses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a measurement device of the presentinvention for use with one fluid;

FIG. 2 is a perspective view of a measurement device of the presentinvention for use with two fluids;

FIG. 3 is a perspective view of a measurement device of the presentinvention with dispenser tip positioning;

FIG. 4 is a perspective view of a measurement device of the presentinvention with multiple capillaries;

FIG. 5 is a perspective view of a measurement device of the presentinvention with use in conjunction with an automatic reporting device;

FIG. 6 is a section view of a measurement device of the presentinvention showing the fluid pathway;

In FIG. 7 there is shown a cross section view of the measurement devicewith features for the positioning of dispensing devices;

In FIG. 8 there is shown a piece of the measurement device forpositioning the tip of the dispensing device at the opening of thecapillary;

FIG. 9 shows several versions of the capillary, including straight,coiled, chambered, and shaped for visual magnification;

FIG. 10 shows the device and a complementary instrument for reading thedevice;

FIG. 11 is a view of a device in which the well moves into proximitywith the inlet of the capillary.

FIG. 12 is a view of a device in which there is an open space acting asa window to view the capillary.

FIG. 13 is a view of a device in which there is a lens to enlarge theview of the capillary.

FIG. 14 is a view of a device with a recess for viewing the capillary.

FIG. 15 is a view of a device with lines to provide a visual reading ofaccuracy and a quantity of dye that is shown to match the volumemeasured by the device.

FIG. 16 is a view of a device with lines to provide a visual reading ofaccuracy and a quantity of dye that is shown to be greater than thevolume measured by the device.

FIG. 17 is a view of a device with lines to provide a visual reading ofaccuracy and a quantity of dye that is shown to be less than the volumemeasured by the device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the invention in more detail, in FIG. 1 there is showna measurement device containing a capillary (4) extending from thefunnel shaped well (2) toward and beyond a viewing window, which may bea magnifying lens (3). The proximal end of the capillary is the inletend by the funnel shaped well. The fluid to be dispensed can becollected from the reservoir (1) by a dispensing device such as apipette or micropipettor. This fluid can contain a dye for betterviewing, and the reservoir may be filled with a sufficient amount offluid or dye and sealed during manufacture of the measurement device.FIG. 2 shows an optional additional reservoir (5) for a secondaryliquid. This secondary liquid can be used to fill the funnel shaped well(2) so long as the secondary liquid is not attracted to the capillary.The secondary liquid can then be used to prevent attraction between thefluid being measured and the measuring device material.

In FIG. 3 there is shown a measurement device with a v-shaped contour(6) and inverted v-shaped aperture (8) for positioning of the dispensingdevice toward the capillary (4). The v-shaped contour (6) is located onthe top edge of the well and enables the dispensing device or pipettetip to rest upon it. The tip is then pushed at an angle toward thecapillary until it encounters the inverted v-shaped aperture (8). As thecenter of gravity of the dispensing device is located at some pointoutside of the positioning features, gravity assists in holding thedispensing device in the two positioning v-shapes. This facilitates thenecessary positioning of the dispensing device for correct functioningof the measurement device. The top surface of the housing includes anon-magnifying viewing window (7) at the region near the desiredmeasurement. The bottom surface of the housing (9) includes v-shapedstandoffs for supporting the capillary (4).

Measuring devices for different volumes could have wells of differentsizes and shapes. Measuring devices for use with different pipette tipscould have wells with different contours (6).

Liquid by the inlet of the capillary will be drawn into the capillary bysurface tension. If the liquid in the well is in one continuous aliquot,the entire aliquot of liquid will be drawn into the capillary. Forexample, if the capillary is hydrophilic and if the well in themeasuring device is hydrophobic, an aqueous solution in the well will bedrawn into the capillary. Glass and fused silica, common materials forcapillaries, are typically hydrophilic. In addition, many capillariesare available with hydrophilic coatings, by companies such as theDrummond Scientific Company. Most petroleum based plastics, includingpolypropylene, polystyrene, and many materials commonly used ininjection molding, are hydrophobic.

The capillary in FIG. 3 is shown to be at a slight incline of 3 degrees.This ensures that the aliquot will remain at the proximal or inlet endof the capillary. Surface tension prevents the aliquot of measuringliquid from flowing out of the inlet. Thus by knowing the position ofthe inlet end of the capillary and the location of the meniscus, thelength of the aliquot of liquid is thus known, too. By knowing theinside diameter of the capillary, or the cross-sectional area as afunction of position along the capillary, the volume of liquid in thecapillary can be calculated.

In FIG. 4 there is shown a measurement device with a plurality ofcapillaries, wells (2), reservoirs (1) and magnifying lenses (3) orwindows to permit measurement of multi-channel dispensing devices suchas multi-channel hand held pipettors or pipetting robots. Additionally,FIG. 4 shows a multi-channel measurement device that can be broken apartdue to spaced cuts (10) in the housing. With multi-channel pipettorsavailable for different numbers of channels, the measuring device canthen be matched to the pipettor or even to just one channel by snappingthe remaining material not already cut or removed during manufacturing.The multi-channel measurement device can be of a SBS compatible spacingand geometry so that it can be used with commonly available dispensingdevices. Conversely, multiple single or multiple channel measuringdevices could be linked together, through interlocking tabs, springtabs, or equivalent means.

In FIG. 5 there is shown an instrument (11) which interfaces with themeasuring device in order to produce a digital measurement from thelocation of the fluid in a capillary or capillaries. This instrument(11) can then document the measurement by either sending the data to acomputer (13) or directly to a printer (14) or recording the informationonto a storage device, such as a memory stick. FIG. 10 shows a differentperspective of the instrument (11) with sensors (22) that are positionedto align with windows (21) in the measuring device, whereby each windowallows the sensor to monitor the liquid or liquid/air interface in thecapillaries inside the measuring device. Note that the base with thesensors could have the geometry, including the shape of the bottom andsides, and also the location of the wells and reservoirs of a standardmicrotiter plate, as could the measuring device. This ensures that thebase and the measuring device could easily interface with roboticsystems. Note that the sensor may be able to determine the volume ofliquid in the capillary without markings on the capillary, simply byknowing the precise location of the inlet end of the capillary, theinternal diameter of the capillary, and the location of the meniscus.This can be accomplished if the capillary is accurately positioned withrespect to the measuring device and the measuring device is accuratelypositioned with respect to the base with the sensors, or if the basewith the sensors can determine the location of the inlet end of thecapillary, such as with an optical window or mechanical stop, or if theliquid in the capillary is not confined to one end and the base cansense the location of the meniscus at both ends of the liquid plug inthe capillary. If the measuring device has an identification code, thesensing device could correlate the measurement data with the measuringdevice.

In FIG. 6 there is shown a cross section view of the measurement devicethat clearly shows the path of the measurement fluid in the capillary(4) from a funnel shaped well (2) toward the viewing lens (3). Thecapillary (4) does not need to be located at the bottom of the funnelshaped well (2), but may be located at some height above the bottom. Thecapillary (4) can be located at a distance from the bottom of the funnelshaped well (2) of approximately one half of the diameter of a sphericalamount of liquid of the measurement volume. Additionally, there are oneor more reservoirs (1) for holding measurement fluid and possibly asecondary fluid to prevent the measurement fluid from being attracted tothe walls of the well (2). Alternatively, the proximal end of thecapillary (4) could be located further from the well (2), the distal endof the capillary (4) could extend beyond the cartridge. The user couldslide the capillary (4) towards the towards the well (2), therebyproviding a means for moving the capillary 4) and well (2) towards eachother.

In FIG. 7 there is shown a cross section view of the measurement devicewith features for the positioning of a dispensing device. The top of themeasuring device has a v-shaped contour for the dispensing device to sitin, with the assistance of gravity. An inverted v-shaped aperture asseen in more detail in FIG. 8 holds the dispensing device close to theend of the capillary to further assist transferring fluid from thedispensing device to the inlet opening of the capillary. The inlet endof the capillary (4) is flush with the bottom surface of the recess inthe plate, to ensure that the liquid contacts the capillary, yet theexternal cylindrical surface of the capillary is not exposed andhindering the dispensed liquid from entering the capillary. Thesefeatures may hold the dispensing device at an angle so that fluid can betransferred to the capillary while any dispensed or aspirated air canseparate from the liquid and will not enter the capillary.

In another embodiment, as shown in FIG. 11, the pipettor dispenses themeasuring liquid into the well, and then the well is pivoted intoproximity with the inlet of the capillary (4), also called the proximalend, thereby providing a means for moving the capillary (4) and wellcloser to each other. The well may be, but is not limited to, a conoidor hemisphere in shape. The well will be positioned such that in itsresting position, it lies with its opening facing toward the top of themeasuring device, or in another position that may facilitate access witha pipet tip. This has two advantages: the user can dispense liquid intoa horizontal well; and any extra spurts of air will be released whilethe well is far from the inlet of the capillary (4) and will thus notaffect the results. Surface tension holds the liquid in the well, evenas the well is pivoted into a vertical position.

As the measuring liquid in the well comes into contact with thecapillary inlet, surface tension draws all of the liquid from the wellinto the capillary. When the pivot well plate (23) is rotated using thehandle (24), the well is brought in proximity to the inlet of thecapillary, it will be positioned so that the inlet is within thedispensed droplet but not entirely pressed against the wall of the well.The pivot may be designed such that it will come into contact withphysical stops or other tactile feedback when the well is in the idealposition relative to the inlet of the capillary.

Various capillary versions are shown in FIG. 9, which illustrate thatthe capillary can be straight, or to save space or possibly for otherreasons, can be shaped in a coil (18), or can have a chamber (19) with along neck. The circumference of the capillary can also be shaped (20) tomake it easier to visualize the meniscus. Markings on the capillary (17)can be opaque, translucent, molded, or engraved. The two markings shownwould form a region indicating that if the meniscus falls in this regionthat the liquid volume is near the desired amount. The measuring devicecould have markings as well or in replacement for markings on thecapillary. Multiple markings on the measuring device or on the capillarycould be used to indicate a range of acceptable variation from a desiredvolume, or possibly be used for calibration.

The measuring device may contain one capillary, or it may contain aplurality of capillaries, either of the same or different sizes.Different sizes would allow for rapid testing of different volumes. Aplurality of capillaries of the same size would allow for multiple testsof the same volume range or the testing of multi-channel pipettes orrobotic liquid dispensers. The measuring device could be in the sameformat as microtiter plates, such as 96 or 384 well plates or could bein partially the same format, such that one or more rows of wells may bepresent, omitting some of the 24, 96, 384, 1536 or other amount ofwells.

The capillaries could be replaceable. For example, if they were trappedin place with a spring tab, a user could replace the capillary. Thiswould be for saving cost, since only the capillary would be replaced,and not the entire measuring device after each use.

The capillaries could be movable, so that they are not initiallycontiguous with the well. After the user dispenses the measuring liquidinto the well, the user could move a handle thereby moving a mechanism,such as a 4 bar linkage system, that moves the capillary into position.Alternatively, the capillary could be laterally positioned by one ormore holes and grooves. A spring tab could apply a slight pressure onthe capillary to lightly hold it in place. Once the measuring liquid isdispensed into the well, The user could slide the capillary toward thewell, so that its inlet is in contact with the measuring liquid.

The capillary in the measuring device could be transparent ortranslucent, made of glass or fused silica or clear plastic,manufactured by machining, casting, molding, or extruding, possibly withan inlet side designed to assist a user to position a pipette tip withrespect to the capillary, or designed to position a drop of liquiddispensed from the pipette tip. Transparent or translucent means withrespect to the optical wavelength being used for detection. Dependingupon the dye, this could use visible, infra red, or ultraviolet light.Other sensing methods could include sensing the position of the liquidusing sensors measuring capacitance, impedance, electrochemicalproperties, surface acoustic wave, surface plasmon resonance,temperature sensor, or other optical means such as detecting changes orvalue of refractive index, dielectric strength, or conductivity. Themeasuring liquid could contain a fluorescent dye to facilitatediscerning the liquid/air interface. A light in the measuring device orprojected through a window or lens, might assist in discerning theliquid/air interface.

The capillary could be coated or surface treated to make the surfacesparticularly hydrophobic, hydrophilic, lipophobic, lipophilic, and/orother analogous property. The capillary can be hydrophilic while thewell region of the device is hydrophobic, thereby encouraging thedispensed liquid to enter the capillary. Alternatively, the capillarycould be lipophilic while the entrance region could be lipophobic andthe liquid being dispensed could be oil or lipid based. Alternatively,the well region could be filled with an oil or lipid and the capillarycould be lipophobic and hydrophilic, thereby an aqueous liquid would bedispensed by the pipette and not stick to the walls of the well regionof the device because they are coated with the lipid or oil. Or viceversa, the capillary could be hydrophobic but lipophilic and the wellregion could contain an aqueous solution that does not enter thecapillary, yet a small volume of lipid or oil dispensed into a funnelshaped region, or other geometrically shaped region to lead the dropletto the entrance of the capillary, would make contact with the capillary.Since the capillary has lipophilic surfaces, surface tension would drawthe drop of dispensed liquid into the capillary.

The surfaces of the measurement device may consist of or be coated inhydrophilic or hydrophobic plastic or other material. For instance, thewell area of the measurement device device could be made substantiallyhydrophobic by plasma treating of a plastic in order to allow an aqueousmeasurement fluid to more completely enter the capillary.

The capillary could be coated or surface treated to react to thedispensed liquid. For example, a color change could indicate where theliquid is present. The shape of the capillary, such as (20) shown inFIG. 9, could aid in visually determining the location of the meniscus.

Placing the capillary at a slight angle or with a slight taper ininternal diameter would ensure that the liquid plug did not travel upthe capillary and distort the determination of the volume of liquid.Alternatively, the capillary could be shaped to encourage the liquidplug to travel to a specific region of the capillary. The capillarycould be positioned at an angle different than horizontal in order toencourage better placement of the measurement fluid.

The capillary may be oriented vertically, so that gravity assists theflow of the measurement fluid downward into the capillary. Similarly,centripetal force may also be used to assist the flow of the measurementtube into the capillary. The exhaust end of the capillary may be open tothe air or sealed with a hydrophobic surface such as hydrophobicpolypropylene weave.

The internal volume or cross-sectional area of each capillary could bemeasured for more accurate results. Graduations or markings on or nearthe capillary could be adjusted to account for the internal volume ofthe specific capillary. The capillary could be tracked, such as by anidentification number, and the specific measurements for that capillarycould be used for the determination of the volume of the dispensedliquid.

By including graduations on or adjacent to the capillary, and by knowingthe internal volume of the capillary from the inlet to each graduation,and by using a liquid such that the meniscus between the liquid and airis discernible, the volume of liquid in the capillary can be determinedby someone observing the capillary or by sensors in the measuring deviceor an attached device. Likewise, sensors in known locations with respectto the capillary can determine the volume without graduations present.

The measuring device could be designed for the user to visuallydetermine if a pipette is within calibration standards. This could bedone by having two lines (17 in FIG. 9) or otherwise demarcated regionin the capillary. If the meniscus falls in this region, then thismeasuring device would validate that the pipette is still withincalibration standards.

Alternatively, the measuring device could fit onto an instrument thatsenses the volume of liquid in the device or the location of themeniscus. In one embodiment, the instrument observes the location of themeniscus and the demarcated regions in each capillary using imageprocessing. In another embodiment, the instrument determines the errorin the dispense volume and sends the suggested correction to the roboticdispenser or displays or prints the suggested correction to the personcalibrating the pipette.

The pipette tip could be positioned so that as liquid is dispensed fromthe pipette tip, the liquid contacts the surface of the capillary and isthen drawn into the capillary by surface tension forces. This could beaccomplished using V-grooves, such as two V-grooves, possibly with oneinverted or oblique with respect to the other. This could beaccomplished with funnels or rings or portions there of or otherfeatures to limit the placement of the pipette or pipette tip.Alternatively, custom dispense tips or pipette tips could be used withfeatures to guide, place, or lock the pipette tip in a particularlocation. For example, the pipette tip could have a collar, whereby thecollar provides a mechanical stop against a boss on the measuringdevice, for placing the tip the correct distance from a wall of thewell. As another example, a recess in the pipette tip could mate with aridge on the measuring device, thereby aiding the user in positioningthe pipette tip with respect to the well.

The dispensed liquid could first touch a surface other than thecapillary, and still rely upon surface tension to draw in the entirevolume of liquid once the drop of liquid spreads out and does contactthe capillary.

If a channel is used, the well region could have a catch basin or hoppertype geometry to conduct the liquid into the rest of the channel. If anaqueous liquid is used and the channel is hydrophilic, or if an oilyliquid is used and the channel is lipophilic, surface tension would drawthe liquid from the wider well region to the narrower channel, and thevolume of the hopper or catch basin would not come into consideration.Alternatively, the channel could be designed so that the liquid remainsand fills the catch basin or hopper region, and the volume of liquid inthis region would be known. A combination of the two could also exist,in which the liquid would remain in only a portion of the catch basin orhopper region.

If the measuring device contains a well region that funnels down insize, thereby directing the dispensed liquid toward the inlet of thecapillary with the well walls that are hydrophobic or lipophobic, or atleast less hydrophilic or lipophilic than the capillary, then once theliquid drop touches the capillary, it would be pulled inside. In thiscase, the capillary needs to be placed where the liquid drop will touchit. For example, if a drop of liquid would tend to form a 2 mm diametersphere, then the center of the capillary should be about 1 mm above thefloor of the well, and the well should not be much larger than 2 mm indiameter, thus ensuring that the drop touches the capillary.

The advantages of the present invention include, without limitation, thefast and inexpensive verification of the continued accuracy of acalibrated liquid dispensing device. Additionally, repeat tests can beused to determine the repeatability of the dispensing device both at thesame volume and at many different volumes. The fluid for measurement canbe included with the measurement device.

While the foregoing written description of the invention enables one ofordinary skill to make and use what is considered presently to be thebest mode thereof, those of ordinary skill will understand andappreciate the existence of variations, combinations, and equivalents ofthe specific embodiment, method, and examples herein. The inventionshould therefore not be limited by the above described embodiment,method, and examples, but by all embodiments and methods within thescope and spirit of the invention.

The invention claimed is:
 1. A liquid measurement device for verifyingthe calibration of a pipettor or other fluid dispenser of volumes up to200 microliters, comprising: a. a well for receiving liquid from saidfluid dispenser; b. a capillary positioned so that its proximal end isfacing said well; c. said capillary having an opening at its proximalend; d. said capillary having an internal hydrophilic surface and adiameter capable of drawing aqueous liquid from said well using surfacetension when said capillary and said well are positioned close to or incontact with each other; e. said capillary positioned at an incline withits proximal end lower than its distal end; f. a viewing area at apreselected region along the length of said capillary enabling a user todetermine the volume of liquid drawn into said capillary; g. said wellhaving a hydrophobic surface; h. said well in a horizontal position toreceive liquid; and i. a pivot, a four-bar linkage, or a slide formoving said well or said proximal end of said capillary to within 0.5 mmof each other.
 2. The liquid measurement device of claim 1, wherein saiddevice contains a magnifying lens at its viewing area.
 3. The liquidmeasurement device of claim 1, wherein said capillary contains markingsto delineate predetermined volumes of liquid.
 4. The liquid measurementdevice of claim 1, wherein said device contains a sensor to indicatewhether the volume of liquid drawn into said capillary is within a rangeof predetermined volumes.
 5. The liquid measurement device of claim 1,wherein said device contains an additional reservoir capable of storingliquid to be measured.
 6. The liquid measurement device of claim 5,wherein said reservoir contains a colored liquid to allow for distinctidentification of said liquid to be measured.
 7. The liquid measurementdevice of claim 1, wherein said device contains one or more V-shaped orinverted V-shaped structures to support said fluid dispenser while it isdispensing fluid into said well.
 8. The liquid measurement device ofclaim 1, wherein said device contains a plurality of said capillaries ofthe same or different size, and a plurality of said wells in aone-to-one correspondence.
 9. The liquid measurement device of claim 8,wherein said device has a housing with multiple channels, each saidchannel having one capillary and one well and each said channel capableof being separated from an adjacent channel.
 10. The liquid measurementdevice of claim 8, wherein said device is configured to be compatiblewith laboratory instrumentation for use with standardized microtiterplates.
 11. The liquid measurement device of claim 1, wherein saiddevice has a module to be placed on the tip of said pipettor or fluiddispenser that will guide, place or lock said pipettor or fluiddispenser in a predetermined location relative to said well.
 12. Theliquid measurement device of claim 9, wherein each said capillary has adifferent size.